ACE is primarily ordered to help diagnose and monitor sarcoidosis. It is often ordered as part of an investigation into the cause of a group of troubling chronic symptoms that may or may not be due to sarcoidosis. ACE will be elevated in 50% to 80% of patients with active sarcoidosis. Concentrations of ACE tend to rise and fall with disease activity. If it is initially elevated in someone with sarcoidosis, ACE can be ordered at regular intervals to monitor the course of the disease and the effectiveness of corticosteroid treatment.

ACE is ordered when you have signs or symptoms such as granulomas, a chronic cough or shortness of breath, red watery eyes, and/or joint pain that may be due to sarcoidosis or to another disorder. This is especially true if you are between 20 and 40 years of age, when sarcoidosis is most frequently seen. Your doctor may order ACE, along with other tests such as an AFB culture or sputum culture (tests that can detect mycobacterial and fungal infections), when he wants to differentiate between sarcoidosis and another granulomatous condition.

If you have been diagnosed with sarcoidosis and your initial ACE levels were elevated, your doctor may order ACE testing at regular intervals to monitor their change over time.

In a diagnostic setting, if ACE levels are high, other diseases have been ruled out, and you have clinical findings consistent with sarcoidosis, then it is likely that you have an active case of sarcoidosis. The finding of a high ACE level helps to confirm the diagnosis. However, sarcoidosis can be present without elevated ACE levels, so a normal ACE level cannot be used to rule out sarcoidosis. Findings of normal ACE levels in sarcoidosis may occur if the disease is in an inactive state, may reflect early detection of sarcoidosis in which the levels of ACE produced are not yet high enough to be abnormal, or may be a case where the cells do not produce increased amounts of ACE. ACE levels are also less likely to be elevated in cases of chronic sarcoidosis.

After diagnosis, ACE levels may be measured to monitor the course of the disease. When initially high levels of ACE are observed to decrease, this usually indicates spontaneous or therapy-induced remission and a favorable prognosis. Rising levels of ACE, on the other hand, may indicate either an early disease process that is progressing or disease activity that is not responding to therapy.

ACE conversion of angiotensin I to angiotensin II is a normal regulatory process in the body. This process has been targeted by the development of drugs called ACE inhibitors that are commonly used in treating hypertension and diabetes. These drugs inhibit the conversion process, keeping the blood vessels more dilated and the blood pressure lower. ACE inhibitors are useful in managing hypertension, but they are not monitored with ACE blood tests. They may, however, interfere with ACE measurements ordered for other reasons.

Hemolysis and hyperlipidemia in the blood sample may falsely decrease ACE levels. Decreased ACE levels may also be seen in patients with:

• Chronic obstructive pulmonary disease (COPD)
• Cystic fibrosis
• Emphysema
• Lung cancer
• Starvation
• Steroid drug therapy
• Hyperthyroidism

ACE has been found in moderately increased levels in a variety of diseases and disorders such as:

• HIV
• Histoplasmosis (fungal respiratory disease)
• Diabetes mellitus
• Hyperthyroidism
• Lymphoma
• Alcoholic cirrhosis
• Gaucher’s disease (a rare inherited lipid metabolism disorder)
• Tuberculosis
• Leprosy

The ACE test, however, is not routinely used to diagnose or monitor these conditions (it has not been shown to be clinically useful).